Method of using a split winglet

ABSTRACT

A method of using a split winglet includes providing an aircraft having a winglet attach fitting attaching a split winglet to a wing. The split winglet has an upper winglet and a lower winglet. The method additionally includes maintaining the winglet attach fitting and winglet at a first height relative to a fuselage when the aircraft is non-flying, and moving the winglet attach fitting and winglet to a second height relative to the fuselage when the aircraft is flying, the second height being higher than the first height.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional application of and claimspriority to pending U.S. application Ser. No. 15/244,896 filed on Aug.23, 2016, and entitled METHOD FOR ATTACHING A SPLIT WINGLET TO A WING,which is a divisional application of and claims priority to U.S. Pat.No. 9,452,825 issued on Sep. 27, 2016, and entitled WINGLET ATTACHFITTING AND METHOD FOR ATTACHING A SPLIT WINGLET TO A WING, the entirecontents of the above-referenced application and patent are expresslyincorporated by reference herein.

FIELD

The present disclosure relates generally to wing tip devices and, moreparticularly, to a winglet attach fitting for attaching a split wingletto an aircraft wing.

BACKGROUND

Winglets may be included on the wing tips of an aircraft to reduceaerodynamic drag generated by the aircraft wings as the wings movethrough the air. Winglets effectively increase the length of thetrailing edge of the wings which spreads out the distribution ofvortices that are shed by the trailing edge and the wing tips. Theredistribution of vortices along the wing trailing edge may result in asignificant reduction of induced aerodynamic drag which may improve theperformance of the aircraft.

A winglet may be provided as a single winglet extending upwardly from awing tip. A winglet may also be provided as a split winglet having anupper winglet and a lower winglet extending respectively upwardly anddownwardly from the wing tip. A winglet must be coupled to the wingstructure in a manner capable of resisting bending loads at thewinglet-wing tip juncture.

Occasionally, it may be necessary to remove a winglet from an aircraft,and replace the winglet with a new winglet of the same or differentconfiguration. For a split winglet, it may be desirable to remove andreplace only the lower winglet, or it may be desirable to remove andreplace only the upper winglet. Unfortunately, conventional means forattaching winglets may require a significant amount of time forinstallation, removal, and replacement. In addition, conventional meansfor installation, removal, and replacement of a winglet may entailcomplex operations that may require partial disassembly of the wing atthe winglet-wing tip juncture in order to remove and reinstall awinglet.

As can be seen, there exists a need in the art for a system forattaching a winglet to a wing that allows for installation, removal, andreplacement of the winglet in a reduced amount of time and without theneed for partial disassembly of the wing.

SUMMARY

The above-noted needs associated with the attachment of a winglet to anaircraft wing are specifically addressed and alleviated by the presentdisclosure which provides a winglet attach fitting that may include awing attachment portion, an upper winglet attachment portion, and alower winglet attachment portion. The upper winglet attachment portionmay be coupled to the wing attachment portion and may be configured tosupport an upper winglet. The lower winglet attachment portion may alsobe coupled to the wing attachment portion and may be configured tosupport a lower winglet. The wing attachment portion may be removablyattachable to a wing tip using fasteners. The fasteners may comprisetension fasteners and may be installed from an inboard side of the wingtip.

Also disclosed is an aircraft having a wing including a wing tip and awing skin. The aircraft may include a wing attach fitting having a wingattachment portion, an upper winglet attachment portion, and a lowerwinglet attachment portion. The wing attachment portion may be removablyattached to the wing tip with tension fasteners installed through anaccess panel provided in the wing skin. The tension fasteners may extendthrough an inboard side of the wing tip and may be engaged to the wingattachment portion. The upper winglet attachment portion may be coupledto the wing attachment portion and may support an upper winglet. Thelower winglet attachment portion may also be coupled to the wingattachment portion and may support a lower winglet.

Also disclosed is a method of securing a split winglet to a wing tip ofan aircraft. The method may include fastening an upper winglet to anupper winglet attachment portion of a wing attach fitting having a wingattachment portion. The method may further include fastening a lowerwinglet to a lower winglet attachment portion of the wing attachfitting. The method may additionally include fastening the wingattachment portion to the wing tip using tension fasteners installedfrom an inboard side of the wing tip to secure the split winglet to thewing.

In a further embodiment, disclosed is a method of using a split winglet.The method may include providing an aircraft having a winglet attachfitting attaching a split winglet to a wing. The method may furtherinclude maintaining the winglet attach fitting at a first heightrelative to a fuselage when the aircraft is non-flying. The method mayadditionally include moving the winglet attach fitting to a secondheight relative to the fuselage when the aircraft is flying, and whereinthe second height is higher than the first height.

The features, functions and advantages that have been discussed can beachieved independently in various embodiments of the present disclosureor may be combined in yet other embodiments, further details of whichcan be seen with reference to the following description and drawingsbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of the present disclosure will become moreapparent upon reference to the drawings wherein like numbers refer tolike parts throughout and wherein:

FIG. 1 is a perspective illustration of an aircraft having splitwinglets mounted on the wing tips of the wings;

FIG. 2 is a front view of the aircraft of FIG. 1 illustrating the splitwinglet comprising an upper winglet oriented at a dihedral angle and alower winglet oriented at an anhedral angle;

FIG. 3 is a perspective illustration of an embodiment of the splitwinglet taken along line 3 of FIG. 1 and illustrating the split wingletmounted to a wing tip;

FIG. 4 is an exploded perspective illustration of the winglet of FIG. 3and illustrating a winglet attach fitting for attaching an upper wingletand a lower winglet to the wing tip;

FIG. 5 is a perspective illustration of an embodiment of a wingletattach fitting configured as a single-piece, unitary structure andcomprising a wing attachment portion, an upper winglet attachmentportion, and a lower winglet attachment portion;

FIG. 6 is a further perspective illustration of the winglet of FIG. 5and illustrating a fitting root end for attaching the winglet to a wingtip rib using a plurality of tension fasteners;

FIG. 7 is a cross-sectional illustration of a portion of an embodimentof an upper winglet taken along line 7 of FIG. 3 and having an upperwinglet forward spar, an upper winglet mid spar, and an upper wingletaft spar;

FIG. 8 is a cross-sectional illustration of the upper winglet takenalong line 8 of FIG. 3 and illustrating the interconnection of the upperwinglet attachment portion to the upper winglet using a plurality ofshear fasteners;

FIG. 9 is a cross-sectional illustration of the split winglet attachedto a wing tip using the winglet attach fitting of FIG. 5 andillustrating the tension fasteners installed from the inboard side ofthe wing tip for fastening the wing attachment portion to the wing tiprib;

FIG. 10 is a perspective illustration of an underside of the wing takenalong line 10 of FIG. 2 and illustrating an access panel allowing forone-sided-access to the wing interior for installing the tensionfasteners securing the winglet to the wing tip;

FIG. 11 is a perspective illustration of a further embodiment of thewinglet attach fitting comprising an upper bracket and an upper wingletattachment portion hingedly coupled to a lower bracket and a lowerwinglet attachment portion;

FIG. 12 is a perspective illustration of the wing attachment portion ofthe winglet attach fitting of FIG. 11;

FIG. 13 is a cross-sectional illustration of the split winglet attachedto a wing tip using the winglet attach fitting of FIG. 11 andillustrating the tension fasteners fastening the wing attachment portionto the wing tip rib;

FIG. 14 is a perspective illustration of a further embodiment of thewinglet attach fitting wherein the wing attachment portion, the upperwinglet attachment portion, and the lower winglet attachment portion areseparate components configured to be coupled together using shear pins;

FIG. 15 is a top view of the winglet attach fitting of FIG. 14 andillustrating the wing attachment portion fastened to the wing tip rib;

FIG. 16 is a perspective view of the wing attachment portion of thewinglet attach fitting of FIG. 14 illustrating an arresting featureincorporated into the wing attachment portion;

FIG. 17 is a side view of the wing attachment portion of the wingletattach fitting of FIG. 14;

FIG. 18 is a perspective view of a root portion clevis of the fittingroot end coupled to an upper lug of the upper winglet attachmentportion;

FIG. 19 is a sectional view taken along line 19 of FIG. 18 andillustrating the center pin coupling the root portion clevis to theupper lug;

FIG. 20 is a perspective view of the wing attachment fitting in anembodiment wherein the fitting root end is integrally formed with thewing tip rib;

FIG. 21 is a top view of the wing attach fitting of FIG. 20;

FIG. 22 is a perspective illustration of a further embodiment of thewinglet attach fitting having skin splices and spar spices for fasteningthe upper winglet to the wing attachment portion and the upper wingletattachment portion which are formed as a unitary structure, and furtherillustrating a pair of clevis fittings for coupling the lower winglet tothe lower winglet attachment portion using shear pins;

FIG. 23 is a an exploded perspective view of the wing attach fitting,the skin splices and spar splices, and forward and aft clevis fittingsshown in FIG. 22;

FIG. 24 is a cross-sectional illustration of the wing attach fitting ofFIG. 23 coupled to the wing tip rib using tension fasteners, and furtherillustrating the skin splices coupling the upper winglet to the upperwinglet attachment portion, and the clevis fittings coupling the lowerwinglet to the lower winglet attachment portion using shear fasteners;

FIG. 25 is a cross-sectional illustration of the winglet attach fittingtaken along line 25 of FIG. 24 and illustrating the skin splices andspar splices fastened to the upper winglet using shear fasteners;

FIG. 26 is a flow chart illustrating an embodiment of a method forsecuring a split winglet to a wing tip;

FIG. 27 is a flow chart illustrating an embodiment of a method of usinga winglet attach fitting;

FIG. 28 is a flow diagram of an aircraft manufacturing and servicemethodology; and

FIG. 29 is a block diagram of an aircraft.

DETAILED DESCRIPTION

Referring now to the drawings wherein the showings are for purposes ofillustrating various embodiments of the present disclosure, shown inFIG. 1 is a perspective view of an aircraft 100 having a fuselage 102.The fuselage 102 may include a cabin for passengers and flight crew. Thefuselage 102 extends from a nose at a forward end of the aircraft 100 toan empennage 104 at an aft end of the fuselage 102. The empennage 104may include one or more tail surfaces such as a vertical tail 108 (e.g.,a vertical fin) and/or a horizontal tail 106 (e.g., horizontalstabilizers) for directional control and stability of the aircraft 100.The aircraft 100 may further include a pair of wings 112 and one or morepropulsion units. Each wing 112 may include a split winglet 298 mountedon a wing tip 114. Each one of the split winglets 298 may include anupper winglet 300 and a lower winglet 400. The split winglet 298 may bemounted to a wing tip 114 using a winglet attach fitting 150 asdisclosed herein.

Advantageously, the winglet attach fitting 150 is configured to allowfor relatively rapid installation and removal of the entire splitwinglet 298 using a limited number of fasteners such as tensionfasteners 172 (FIG. 4) or other types of threaded fasteners, asdescribed in greater detail below. However, the split winglet 298 may beattached to a wing tip 114 using fasteners that may not be loaded intension. For example, in any one of the embodiments disclosed herein,the fasteners may comprise threaded fasteners loaded in shear (notshown) or fasteners loaded in a combination of shear and tension (notshown) for attaching the split winglet 298 to a wing tip 114.Furthermore, in any one of the embodiments disclosed herein, one or moremechanical features (not shown) may be incorporated into the wingletattach fitting 150 and/or into the wing tip 114 to facilitate theremovable attachment of a split winglet 298 from the wing tip 114 suchas from one side (e.g., an inboard side) of the wing tip 114 without theuse of threaded fasteners.

In an embodiment, the split winglet 298 may be attached to a wing tip114 using mechanical fasteners such as threaded fasteners and includingtension fasteners 172 that may be installed from one side (e.g., aninboard side 134—FIG. 3) of the wing tip 114. For example, threadedfasteners such as tension fasteners 172 of other types of fasteners maybe passed into a wing interior 132 on an inboard side 134 of a wing tip114 to attach the split winglet 298 to the wing tip 114. In a furtherembodiment, the winglet attach fitting 150 may be secured to the wingtip 114 without the need for threaded fasteners. Furthermore,embodiments of the winglet attach fitting 150 advantageously provide ameans for relatively rapid installation, removal, and/or replacement ofthe upper winglet 300 while the lower winglet 400 remains attached tothe wing tip 114, or relatively rapid installation, removal, and/orreplacement of the lower winglet 400 while the upper winglet 300 remainsattached to the wing tip 114.

Although the winglet attach fitting 150 is described in the context ofmounting a split winglet 298 to a fixed wing aircraft such as thetube-and-wing aircraft 100 illustrated in FIG. 1, the winglet attachfitting 150 may be used for mounting a split winglet 298 to any aircraftof any configuration, without limitation. For example, any one of thewinglet attach fitting 150 embodiments disclosed herein may be used formounting a split winglet 298 to civil, commercial, or military aircraft.In addition, any one of the winglet attach fitting 150 embodimentsdisclosed herein may be used for mounting a split winglet 298 toalternative aircraft configurations, and are not limited to thetube-and-wing aircraft 100 configuration illustrated in FIG. 1. Forexample, the winglet attach fitting 150 may be used for mounting a splitwinglet 298 to hybrid wing-body aircraft or to a blended-wing aircraft.In addition, any one of the winglet attach fitting 150 embodimentsdisclosed herein may be used for mounting a split winglet 298 toalternative types of aerodynamic surfaces including, but not limited to,a horizontal stabilizer, a canard, or any other type of aerodynamicsurface.

Referring to FIG. 2, the upper winglet 300 may have an upper wingletroot 304 and an upper winglet tip 306. The upper winglet root 304 may beaffixed to or fastened to the winglet attach fitting 150. The upperwinglet 300 may extend upwardly from the wing 112 of the aircraft 100and may be oriented at a dihedral angle 302 relative to horizontal. Inan embodiment, the upper winglet 300 may be oriented at a dihedral angle302 of at least approximately 60 degrees relative to horizontal when thewing 112 is under an approximate 1-g flight loading wherein the wing 112may deflect upwardly. However, the upper winglet 300 may be oriented ata dihedral angle 302 of less than approximately 60 degrees relative tohorizontal under an approximate 1-g flight loading. In an embodiment,the upper winglet 300 may be oriented at a dihedral angle 302 of fromapproximately 45 degrees to 80 degrees relative to horizontal. Forexample, the upper winglet 300 may be oriented at a dihedral angle 302of approximately 60 degrees, plus or minus 5 degrees, relative tohorizontal when the wing 112 is under an approximate 1-g flight loading.

In FIG. 2, the lower winglet 400 may have a lower winglet root 404 and alower winglet tip 406. The lower winglet root 404 may be affixed orotherwise coupled to the winglet attach fitting 150. The lower winglet400 may extend downwardly from the wing 112 of the aircraft 100 and maybe oriented at an anhedral angle 402 relative to horizontal when thewing 112 is under an approximate 1-g flight loading wherein the wing 112may deflect upwardly. In an embodiment, the lower winglet 400 may beoriented at an anhedral angle 402 of up to approximately 30 degrees ormore. For example, in an embodiment, the lower winglet 400 may beoriented at an anhedral angle 402 of approximately 15 degrees, plus orminus 5 degrees, relative to horizontal when the wing 112 is under anapproximate 1-g flight loading. However, the lower winglet 400 may beoriented at any anhedral angle 402. Although shown as relativelystraight members extending from the winglet root 304, 404 to the winglettip 306, 406, the upper winglet 300 and/or the lower winglet 400 may beprovided in a non-straight shape and may include curved shapes orcontoured shapes and may further include combinations of straightshapes, curved shapes, and contoured shapes.

Referring to FIG. 3, in an embodiment, the lower winglet root 404 mayintersect or may be joined with the upper winglet root 304 (FIG. 4) atthe winglet attach fitting 150. In an embodiment, the leading edge ofthe upper winglet 300 (FIG. 4) and/or the leading edge of the lowerwinglet 400 may intersect the wing tip 114 at a location that isapproximately coincident with the wing leading edge, or at a locationthat is generally aft of the wing leading edge. Likewise, the trailingedge of the upper winglet 300 and/or the trailing edge of the lowerwinglet 400 may intersect the wing tip 114 at a location that isapproximately coincident with the wing trailing edge, or at a locationthat is generally aft of the wing trailing edge.

In FIG. 3, in an embodiment, the split winglet 298 may be configuredsuch that the upper winglet root chord and/or the lower winglet rootchord may be approximately the same length as the wing tip chord. Forexample, in an embodiment, the upper winglet root chord and/or the lowerwinglet root chord may each have a length in the range of fromapproximately 60 to 100 or more percent of the length of the wing tipchord. In this regard, the split winglet 298 may be configured such thatthe upper winglet root chord and/or the lower winglet root chord may belonger or shorter than the wing tip chord.

Referring to FIG. 4, shown is an exploded view of the split winglet 298illustrating the interconnection of the upper winglet 300 and the lowerwinglet 400 to the wing tip 114 using the winglet attach fitting 150. Inthe embodiment shown, the winglet attach fitting 150 may be configuredas a single-piece fitting which may be machined, cast, and/or otherwiseformed as a unitary structure 192 and which may have a generallyV-shaped cross section. The winglet attach fitting 150 includes a wingattachment portion 152 having a fitting root end 154 (FIG. 9) configuredto be removably fastened to a wing tip 114. For example, the fittingroot end 154 may be directly coupled to a wing tip rib 128.

In an embodiment, the wing attachment portion 152 may be disposed inabutting contact with the wing tip rib 128 and may be fastened theretoby means of tension fasteners 172 (FIG. 9) or other types of fasteners(e.g., shear fasteners). For example, fasteners may be extended throughthe wing tip rib 128 from an inboard side 134 (FIG. 3) thereof. Thetension fasteners 172 or other types of fasteners may directly engagethe winglet attach fitting 150. For example, tension fasteners 172 orother types of fasteners may be threadably engaged to a correspondingquantity of threaded bores (not shown) that may be formed in the wingletattach fitting 150. Fasteners such as tension fasteners 172 and/or shearfasteners 174 may also be installed from an outboard side of the wingtip 114 to attach the split winglet 298 to the wing tip 114. Fastenersmay also be threadably engaged to threaded receptacles (not shown) suchas may be mounted to the winglet attach fitting 150. In an embodimentshown in FIG. 9, tension fasteners 172 or other types of fasteners maybe threadably engaged to a corresponding quantity of barrel nuts 168(FIG. 5) that may be contained within or mounted within the barrel nutbores 166 (FIG. 5) formed in the fitting root end 154. In an embodiment,the fitting root end 154 may be integrally formed with the wing tip rib128 in the manner similar to the winglet attach fitting 150 illustratedin FIGS. 20-21 and described below.

In FIG. 4, the wing 112 may include at least one wing spar 116 (FIG. 14)such as a forward wing spar 118 and/or an aft wing spar 120, and one ormore intermediate wing spars (not shown). The wing spars 116 mayterminate at the wing tip rib 128 which may comprise the outermost ribof the wing 112. In an embodiment, the upper wing skin 122 or lower wingskin 124 may include an access panel 126 (FIG. 10) to allow forinsertion of the tension fasteners 172 into a wing interior 132 forinstallation of the tension fasteners 172 through the wing tip rib 128and into threaded engagement with barrel nuts 168 that may be includedwith the wing attachment portion 152. The barrel nuts 168 and tensionfasteners 172 advantageously allow for one-sided installation andremoval of the winglet attach fitting 150 with the upper winglet 300 andlower winglet 400 attached thereto. In this manner, the winglet attachfitting 150 obviates the need to remove the upper winglet 300 or thelower winglet 400 from the winglet attach fitting 150 prior to removingthe split winglet 298 from the wing tip 114.

In FIG. 4, the upper winglet attachment portion 176 and the lowerwinglet attachment portion 184 may be coupled to the wing attachmentportion 152. The upper winglet attachment portion 176 and the lowerwinglet attachment portion 184 may extend from the outboard side 136(e.g., the split winglet 298 side) of the wing attachment portion 152,and in opposing relation to the inboard side 134 (e.g., the wing tip 114side) of the wing attachment portion 152. The upper winglet attachmentportion 176 may extend in upwardly angled relation to the wingattachment portion 152. For example, the upper winglet attachmentportion 176 may extend upwardly from the wing attachment portion 152 atan angle of at least approximately 60 degrees relative to horizontal. Inan embodiment, the upper winglet attachment portion 176 may be orientedat an angle that may be complementary to the dihedral angle 302 (FIG. 2)of the upper winglet 300 which may be oriented at a dihedral angle 302of at least approximately 60 degrees relative to horizontal duringupward deflection of the wing 112 under an approximate 1-g flightloading.

The lower winglet attachment portion 184 may be oriented in downwardlyangled relation to the wing attachment portion 152. For example, thelower winglet attachment portion 184 may extend downwardly at an angleof up to approximately 30 degrees or more relative to horizontal. Theangled orientation of the lower winglet attachment portion 184 may beconfigured complementary to the angled orientation of the lower winglet400 or the lower winglet attachment portion 184 may be aligned with theangled orientation of the lower winglet 400. In an embodiment, the lowerwinglet 400 may be oriented at an anhedral angle 402 (FIG. 2) of up toapproximately 30 degrees or more when the wing 112 is under anapproximate 1-g flight loading as mentioned above. However, the lowerwinglet attachment portion 184 may be oriented at a different angle thanthe lower winglet 400. In an embodiment, the wing attachment portion 152may extend along a lengthwise (e.g., chordwise) direction of at least aportion of the length of the wing tip rib 128. The wing attachmentportion 152 may have a generally vertically-oriented face on a fittingroot end 154 (FIG. 5) for interfacing with a generallyvertically-oriented face of the wing tip rib 128. However, the wingattachment portion 152 and the wing tip rib 128 may be provided withnon-vertical faces for mating with one another.

In FIG. 4, in an embodiment, as indicated above, the upper wingletattachment portion 176 and the lower winglet attachment portion 184 maybe integrally formed with the wing attachment portion 152 to form aunitary structure. The upper winglet attachment portion 176 may have agenerally hollow, box-shaped terminal end 182 (FIG. 5) configured forstove-piping or slidable insertion of the upper winglet attachmentportion 176 into the generally hollow interior of the upper winglet 300at the upper winglet root 304 end. Likewise, the lower wingletattachment portion 184 may have a generally hollow, box-shaped terminalend 190 (FIG. 5) configured for stove-piping the lower wingletattachment portion 184 into the generally hollow interior of the lowerwinglet 400 at the lower winglet root 404 end. In an embodiment, theupper winglet 300 and/or the lower winglet 400 may include one or morewinglet spars 308, 310, 312, 408, 410, 412, that may extend between therespective winglet skins 314, 414. For example, the upper winglet 300may include an upper winglet forward spar 308, an upper winglet mid spar310, and an upper winglet aft spar 312. Likewise, the lower winglet 400may include a lower winglet forward spar 408, a lower winglet mid spar410, and a lower winglet aft spar 412. However, the upper winglet 300and/or the lower winglet 400 may include any number of spars, or theupper winglet 300 and/or the lower winglet 400 may be devoid of spars.

In FIG. 4, the upper winglet 300 and the lower winglet 400 may beattached to the respective upper winglet attachment portion 176 andlower winglet attachment portion 184 using at least one shear fastener174 such as exteriorly-accessible shear fasteners 174. In an embodiment,the shear fasteners 174 may be extended through the respective upperwinglet skin 314 and lower winglet skin 414. For example, the shearfasteners 174 may be threadably engaged into nutplates (not shown) orother threaded receptacles that may be mounted on the interior of thewalls 178 of the terminal end 182 of the upper winglet attachmentportion 176 and lower winglet attachment portion 184. The shearfasteners 174 may also be configured as non-threaded fastenersincluding, but not limited to, blind bolts, rivets, and any other typeof non-threaded, one-sided fasteners. In an embodiment, the wingletattach fitting 150 may be configured to minimize or eliminate the needfor internal access to the winglet attach fitting 150 for installing thetension fasteners 172 attaching the upper winglet 300 and lower winglet400 to the respective upper winglet attachment portion 176 and lowerwinglet attachment portion 184. However, the upper and lower wingletattachment portion 176, 184 may be configured to be mechanicallyfastened to the upper and lower winglet forward spar 308, 408, mid spar310, 410, and/or aft spar 312, 412 as described in greater detail below.

Referring to FIG. 5, shown is an embodiment of a winglet attach fitting150 configured as a unitary structure 192 that may allow forinstallation and removal of the entire split winglet 298 in a reducedamount of time relative to conventional methods for attaching winglets.The upper winglet attachment portion 176 and the lower wingletattachment portion 184 may be joined together at the wing attachmentportion 152 to form the unitary structure 192 winglet attach fitting150. The upper winglet attachment portion 176 and the lower wingletattachment portion 184 may intersect one another at the wing attachmentportion 152. In an embodiment not shown, the winglet attach fitting maybe configured in an arrangement wherein the lower winglet attachmentportion 184 is joined to the upper winglet attachment portion 176 andthe upper winglet attachment portion 176 is, in turn, joined to the wingattachment portion 152. As indicated above, the upper winglet attachmentportion 176 and the lower winglet attachment portion 184 may beconfigured to be insertable into the respective upper winglet 300 andlower winglet 400. The upper winglet attachment portion 176 and thelower winglet attachment portion 184 may be mechanically fastened to therespective upper winglet 300 and lower winglet 400 using shear fasteners174 as indicated above.

FIG. 6 illustrates a fitting root end 154 on an inboard side of thewinglet attach fitting 150 of FIG. 5. The fitting root end 154 may beformed as a relatively thick block with a series of vertically-orientedbarrel nut bores 166 for accommodating barrel nuts 168. Although thebarrel nut bores 166 may be non-vertically oriented, a verticalorientation of the barrel nut bores 166 may facilitate removal andreplacement of barrel nuts 168 from the winglet attach fitting 150. Thefitting root end 154 may further include a corresponding series ofhorizontally-oriented fastener bores 170 that may be aligned with thebarrel nut bores 166. The tension fasteners 172 (FIG. 4) may be extendedthrough the fastener bores 170 in the wing tip rib 128 (FIG. 4) and thefitting root end 154 and threadably engaged to the barrel nuts 168 toattach the winglet attach fitting 150 to the wing tip rib 128.

However, other types of fasteners may be used to attach the wingletattach fitting 150 to the wing tip 128. For example, threaded fastenerssuch as tension fasteners or shear fasteners may be used to attach thewinglet attach fitting 150 to the wing tip rib 128. In an embodiment,the tension fasteners 172 may be engaged to threaded receptacles (notshown) other than barrel nuts 168. For example, the tension fasteners172 may be threadably engaged to threaded bores (not shown) that may beformed directly in the fitting root end 154 of the winglet attachfitting 150. Even further, the tension fasteners 172 may be threadablyengaged to nut plates (not shown) that may be mounted on an outboardside 136 of the wing tip rib 128. However, one or more of the barrelnuts 168 may be removed and replaced in the event of damage to thebarrel nut 168 and thereby avoid the need to replace the entire wingletattach fitting 150 if a threaded bore becomes damaged. Advantageously,the generally vertical orientation of the barrel nut bores 166 may allowfor relatively rapid removal and replacement of one or more barrel nuts168 from the winglet attach fitting 150.

In FIG. 6, in an embodiment, the winglet attach fitting 150 may includea forward tab 162 (FIG. 22) and/or an aft tab 164 extending from arespective forward face 158 and aft face 160 of the winglet attachfitting 150. The forward tab 162 and the aft tab 164 may facilitate theattachment of a relatively small leading edge rib (not shown) ortrailing edge rib (not shown) to the winglet attach fitting 150. Suchleading edge rib and or trailing edge rib may support one or moreaerodynamic fairings (not shown) to provide an aerodynamicallycontinuous surface between the leading edges and the trailing edges ofthe wing 112 (FIG. 4) and the split winglet 298 (FIG. 4).

FIG. 7 is a cross-section of a portion of the upper winglet 300 with thetrailing edge of the upper winglet 300 omitted for clarity. As indicatedabove, the upper winglet 300 may include an upper winglet forward spar308, an upper winglet mid spar 310, and an upper winglet aft spar 312extending between opposing upper winglet skin 314 s. However, the upperwinglet 300 may be provided with any number of spars and is not limitedto the configuration illustrated FIG. 7. As mentioned above, the upperwinglet 300 attach portion may be configured to be mechanically fastenedto the upper winglet skin 314 on opposite sides (i.e., inboard side andoutboard side) of the upper winglet 300. In addition, the upper wingletattachment portion 176 may be configured to be mechanically fastened tothe upper winglet forward spar 308, the upper winglet mid spar 310,and/or the upper winglet aft spar 312 as described below. The lowerwinglet 400 may be configured similar to the upper winglet 300 and mayinclude a lower winglet forward spar 408 (FIG. 4), a lower winglet midspar 410 (FIG. 4), and a lower winglet aft spar 412 (FIG. 4) to whichthe lower winglet attachment portion 184 (FIG. 4) may be fastened.

FIG. 8 is a cross-section of the upper winglet 300 (FIG. 7) showing theinterconnection of the upper winglet attachment portion 176 to the upperwinglet 300. A plurality of shear fasteners 174 may be extended throughthe upper winglet skin 314 and the walls 178 of the upper wingletattachment portion 176. Although not shown, the shear fasteners 174 mayengage nutplates or other threaded receptacles that may be mounted on aninterior of the upper winglet attachment portion 176. As indicatedabove, the shear fasteners 174 may also be configured as non-threadedfasteners such as blind bolts, rivets, and other types of non-threaded,one-sided fasteners, without limitation. The upper winglet attachmentportion 176 may optionally include one or more ribs to provide increasedstructural support and stiffness to the upper winglet attachment portion176. The outer surfaces of the upper winglet attachment portion 176 maybe sized and configured to engage the inner surfaces of the upperwinglet skin 314 with minimal or no shimming.

In an embodiment, the upper winglet attachment portion 176 (FIG. 8) maybe configured to nest against the inner surfaces of the upper wingletforward spar 308 and upper winglet aft spar 312 (FIG. 8). One or moremechanical fasteners may be extended through the upper winglet forwardspar 308 and/or the upper winglet aft spar 312 and into the walls 178 ofthe upper winglet attachment portion 176 and may threadably engagenutplates (not shown) or other threaded receptacles or non-threadedfasteners (e.g., one-sided fasteners) may be used to attach the upperwinglet forward spar 308 and/or the upper winglet aft spar 312 to thewalls 178 of the upper winglet attachment portion 176. The lower winglet400 (FIG. 4) may be fastened to the lower winglet attachment portion 184(FIG. 6) in a manner similar to the fastening of the upper winglet 300to the upper winglet attachment portion 176.

FIG. 9 is a cross-section of the unitary structure 192 winglet attachfitting 150 showing the attachment of the upper winglet 300 to the upperwinglet attachment portion 176 using shear fasteners 174, and theattachment of the lower winglet 400 to the lower winglet attachmentportion 184 using shear fasteners 174. As indicated above, the terminalends 182, 190 of the upper winglet attachment portion 176 and the lowerwinglet attachment portion 184 may each be configured as generallyhollow box-shaped ducts over which the respective upper winglet 300 andlower winglet 400 (FIG. 4) may be fitted. In this regard, the upperwinglet 300 may be stove-piped over the upper winglet attachment portion176, and the lower winglet 400 may be stove-piped over the lower wingletattachment portion 184. The upper winglet attachment portion 176 and thelower winglet attachment portion 184 may have a step 180, 88 machined orformed in the terminal end 182, 190 for abutting the root end of theupper winglet 300 and the root end of the lower winglet 400.

FIG. 9 illustrates the tension fasteners 172 installed from the inboardside 134 of the wing tip 114 for fastening the wing attachment portion152 to the wing tip rib 128. The wing tip rib 128 may include a verticalflange 130 on the upper and lower edges of the wing tip rib 128.Fastener bores 170 may be formed through the vertical flanges 130 inalignment with the fastener bores 170 extending through the fitting rootend 154 of the wing attachment portion 152. Fastener bores 170 may alsobe formed at other locations on the wing tip rib 128.

In an embodiment, one or more discrete fairings (not shown) may beattached to the winglet attach fitting 150 (FIG. 9) and/or upper winglet300 (FIG. 9) and lower winglet 400 (FIG. 4) using small mechanicalfasteners extending through the fairing and engaging small barrel nuts,nutplates, threaded bore, or other threaded receptacles. In this regard,the winglet attach fitting 150 may include a winglet upper inner fairing196 (FIG. 9) and a winglet lower inner fairing 198 mounted on an inboardside 134 of the split winglet 298 for providing an aerodynamicallysmooth transition from the inboard side 134 of the upper winglet 300 andthe lower winglet 400 to the outer mold line of the upper wing skin 122and the lower wing skin 124. Although not shown, the winglet upper innerfairing 196 and the winglet lower inner fairing 198 may be fastenedusing threaded fasteners engaged to nutplates or other threadedreceptacles mounted on an interior of a fairing bracket 200.

The fairing bracket 200 (FIG. 9) may be sandwiched between the fittingroot end 154 and the wing tip rib 128. Alternatively, the outer surfaceof the winglet attach fitting 150 (FIG. 9) may be sized and configuredto function as the fairing between the upper wing skin 122 and upperwinglet skin 314 (FIG. 9) and between the lower wing skin 124 and thelower winglet skin 414. A winglet outer fairing 194 may also beinstalled to provide an aerodynamically smooth transition between theoutboard side 136 (FIG. 9) of the upper winglet skin 314 and theoutboard side 136 of the lower winglet skin 414. However, in anembodiment not shown, the outer surface of the winglet attach fitting150 itself may function act as the fairing between the upper wingletskin 314 and the lower winglet skin 414.

FIG. 10 shows an underside of the wing 112 illustrating an opening 125that may be uncovered by removing an access panel 126 to provide accessto the wing interior 132. The opening 125 may preferably be large enoughto allow for insertion of hand tools for installation and removal of thetension fasteners 172. The access panel 126 facilitates one-sided-accessto the wing interior 132 for installing the tension fasteners 172securing the winglet to the wing tip 114. The tension fasteners 172 maybe threadably engaged to the barrel nuts 168 (FIG. 9) which may beincluded in the barrel nut bores 166 (FIG. 9) formed in the fitting rootend 154 (FIG. 9) of the wing attachment portion 152 (FIG. 9) of thewinglet attach fitting 150 (FIG. 9). In this manner, the winglet attachfitting 150 embodiments disclosed herein provide a means for relativelyrapid installation, removal, and replacement of an entire split winglet298 including the upper winglet 300 and lower winglet. Embodiments ofthe winglet attach fitting 150 described below may allow forinstallation, removal, and replacement of lower winglet 400 (FIG. 4)while the upper winglet 300 remains attached to the wing tip 114, or theinstallation, removal, and replacement of the upper winglet 300 whilethe lower winglet 400 remains attached to the wing tip 114.

FIGS. 11-12 show an embodiment of a winglet attach fitting 150comprising an upper bracket 206 and an upper winglet attachment portion176 hingedly coupled to a lower bracket 208 and a lower wingletattachment portion 184 by means of a hinge joint 204. The wingattachment portion 152 is comprised of the upper bracket 206 and thelower bracket 208 which are separate components. The upper bracket 206may be integral with the upper winglet attachment portion 176. Forexample, the upper bracket 206 and the upper winglet attachment portion176 may be formed as a unitary structure 192. Likewise, the lowerbracket 208 may be integral with the lower winglet attachment portion184. The single piece of the upper bracket 206 and upper wingletattachment portion 176 may be a separate component from the single pieceof the lower bracket 208 and lower winglet attachment portion 184.

In FIGS. 11-12, the single piece of the upper bracket 206 and upperwinglet attachment portion 176 may be hingedly coupled to the singlepiece of the lower bracket 208 and lower winglet attachment portion 184.The upper bracket 206 and the lower bracket 208 may be fastened to thewing tip rib 128 using one or more fasteners such as threaded fasteners(e.g., tension fasteners 174) as mentioned above with regard to FIGS. 4and 9. The fastening of the upper bracket 206 and the lower bracket 208to the wing tip rib 128 may prevent movement of the upper bracket 206and the lower bracket 208 relative to one another. One or more hingepins 212 may be extended through pin bores 202 formed in hinge bosses210 of the upper bracket 206 and lower bracket 208. The hinge bosses 210may be interconnected by the hinge pin 212. The hinge bosses 210 of theupper bracket 206 and lower bracket 208 may mesh with one another toform the hinge joint 204 which may be characterized as a non-rotatablehinge joint 204 when the upper bracket 206 and the lower bracket 208 arefastened to the wing tip rib 128 to retain the upper winglet attachmentportion 176 and the lower winglet attachment portion 184 in fixedrelationship with one another.

The hinge pin 212 may be oriented in a stream-wise direction such asalong a forward direction 110 of the aircraft 100. However, the hingepin 212 may be oriented in any direction. Advantageously, the hinge pin212 allows for removal of the lower winglet 400 (FIG. 4) while the upperwinglet 300 (FIG. 4) remains attached (e.g., fastened) to the wing tip114 (FIG. 9), or removal of the upper winglet 300 while the lowerwinglet 400 remains attached (e.g., fastened) to the wing tip 114.Advantageously, by splitting the winglet attach fitting 150 into twoseparate components, the depth and contour of the cavities of eachcomponent (e.g., the upper bracket 206 and upper winglet attachmentportion 176, and the lower bracket 208 and lower winglet attachmentportion 184) may be minimized to simplify manufacturing or machining.

In FIG. 12-13, shown is the upper bracket 206 and the lower bracket 208which are provided as two separate components. The upper bracket 206 andthe lower bracket 208 may each be configured similar to the fitting rootend 154 shown in FIGS. 5-6 and described above. In this regard, theupper bracket 206 and the lower bracket 208 may each include a series ofbarrel nut bores 166 for accommodating a plurality of barrel nuts 168.Tension fasteners 172 may be extended through the fastener bores 170 inthe wing tip rib 128 and in the upper bracket 206 and lower bracket 208for engaging the barrel nuts 168 contained in the barrel nut bores 166.Alternatively, the winglet attach fitting 150 may include threadedreceptacles other than barrel nuts 168 for receiving the tensionfasteners 172, as indicated above with regard to the winglet attachfitting 150 of FIGS. 5-6 and 9. The upper winglet 300 and the lowerwinglet 400 may be stove-piped onto the respective upper wingletattachment portion 176 and the lower winglet attachment portion 184using shear fasteners 174 in a manner similar to that shown in FIG. 9and described above.

FIG. 14 shows a further embodiment of the winglet attach fitting 150wherein the wing attachment portion 152, the upper winglet attachmentportion 176, and the lower winglet attachment portion 184 comprise three(3) separate components that may be coupled together using shear pins262. In an embodiment, the shear pins 262 may comprise a pair of centerpins 222, a pair of upper shear pins 262 (FIG. 22), and a pair of lowershear pins 262. The upper winglet attachment portion 176 and the lowerwinglet attachment portion 184 may each include at least one lug 234,236. In the embodiment shown, the upper winglet attachment portion 176includes a pair of upper lugs 234 and the lower winglet attachmentportion 184 includes a pair of lower lugs 236. However, the upperwinglet attachment portion 176 may include any quantity of upper lugs234. For example, although not shown, the upper winglet attachmentportion 176 may include an upper lug 234 aligned with the upper wingletforward spar 308, an upper lug 234 aligned with the mid spar 310, and anupper lug 234 aligned with the rear spar 312. Likewise the lower wingletattachment portion 184 may include a corresponding quantity of lowerlugs 236 to match the quantity of upper lugs 234 of the upper wingletattachment portion 176.

The wing attachment portion 152 (FIG. 14) may include at least oneclevis 220 such as a root portion clevis 220 extending outwardly fromthe fitting root end 154 on an outboard side 136 thereof. For example,in the embodiment shown, the wing attachment portion 152 includes a pairof root portion clevises 220 extending outwardly from the fitting rootend 154. However, the wing attachment portion 152 may include anyquantity of root portion clevises 220 to match the quantity of upperlugs 234 and lower lugs 236. In the embodiment shown in FIG. 14, thepair of upper lugs 234 of the upper winglet attachment portion 176 maybe coupled to the pair of root portion devises 220 using at least onepin 222, 230, such as a pair of the upper pins 230 (e.g., forward andaft upper pins 230) and a pair of center pins 222 (e.g., forward and aftcenter pins 222). Likewise, the pair of lower lugs 236 of the lowerwinglet attachment portion 184 may be coupled to the pair of rootportion devises 220 using a pair of the lower pins 232 (e.g., forwardand aft lower pins 232) and the pair of center pins 222 (e.g., forwardand aft center pins 222).

However, the upper pins 230, the lower pins 232, and the center pins 222may be provided in quantities corresponding to the quantity of upperlugs 234, lower lugs 236, and root portion devises 220. For example, theabove-mentioned embodiment having three (3) upper lugs 236, three (3)lower lugs 234, and three (3) devises 220, may also include three (3)upper pins 230, three (3) lower pins 232, and three (3) center pins 222for coupling the lugs 234, 236 to the root portion devises 220.Advantageously, the upper pins 230 may not extend through the lower lug236, and the lower pins 232 may not extend through the upper lug 234. Inthis manner, the upper winglet 300 or the lower winglet 400 may beremoved from the wing attachment portion 152 without removing the wingattachment portion 152 from the wing tip 114. In an embodiment, theupper pins 230, the lower pins 232, and the center pins 222 may beprovided as double-ended studs (not shown).

In an embodiment, the center pins 222 (FIG. 14) and the upper or lowerpins 230, 232 may be sized to function as fuse pins to allow the upperwinglet 300 and/or lower winglet 400 to separate or break away cleanlyfrom the wing attachment portion 152. For example, upon the applicationof a forward load or aft load of sufficient magnitude on the lowerwinglet 400 and/or upper winglet 300 such as may occur during contact ofthe lower winglet 400 and/or operate winglet with an object, the centerpins 222 and upper and/or lower pins 230, 232 may be configured to shearupon the attainment of a predetermined shear load on the center pins 222and upper and/or lower pins 230, 232.

In a further embodiment, the upper winglet attachment portion 176 may bedivided into two separate components (not shown) including one componentthat may be fastened to the upper winglet skin 314 on an inboard side134 of the upper winglet 300 and which may include the portion of theupper lugs 234 that are engageable to the root clevis portion 220 usingthe upper pins 230, and another component that may be fastened to theupper winglet skin 314 on an outboard side 136 of the upper winglet 300and which may include the portion of the upper lugs 234 that areengageable to the root clevis portion 220 using the center pins 222.Likewise, the lower winglet attachment portion 184 may be divided intotwo separate components (not shown) including one component that may befastened to the lower winglet skin 414 on an inboard side 134 of theupper winglet 400 and which may include the portion of the lower lugs236 that are engageable to the root clevis portion 220 using the lowerpins 232, and another component that may be fastened to the lowerwinglet skin 414 on an outboard side 136 of the lower winglet 400 andwhich may include the portion of the lower lugs 236 that are engageableto the root clevis portion 220 using the center pins 222. By dividingthe upper winglet attachment portion 176 into two separate components,machining and assembly of the upper winglet attachment portion 176 tothe upper winglet 300 may be simplified. Such machining and assemblybenefits may also apply to a lower winglet attachment portion 184divided into two separate components.

FIG. 15 shows the wing attachment portion 152 of the winglet attachfitting 150 of FIG. 14 being fastened to the wing tip rib 128 usingtension fasteners 172. The fitting root end 154 may be configuredsubstantially similar to the fitting root end 154 of the winglet attachfitting 150 shown in FIGS. 5-6. The tension fasteners 172 may bethreadably engaged to the barrel nuts 168 in the wing attachment portion152. The arrangement may allow the split winglet 298 to be installedand/or removed from the wing tip 114 as a complete unit.

FIGS. 16-17 illustrate the wing attachment portion 152 of the wingletattach fitting 150 of FIG. 15. Shown is the pair of root portion devises220 extending outwardly from the fitting root end 154. In an embodiment,the wing attachment portion 152 may include one or more arrestingfeatures 238. The arresting feature 238 may prevent free (e.g.,downward) rotation of the upper lugs 234 of the upper winglet attachmentportion 176 and/or the lower lugs 236 of the lower winglet attachmentportion 184 relative to the clevis when the center pin 222 is removedfrom the winglet attachment fitting. In the embodiment shown, thearresting feature 238 comprises a lug bearing portion 240 (FIG. 19) anda clevis bearing portion 242 included with the pair of the upper lugs234, the pair of the lower lugs 236, and the pair of root portiondevises 220.

FIG. 18 is perspective illustration of the coupling of a root portionclevis 220 of the fitting root end 154 to an upper lug 234 of the upperwinglet attachment portion 176. Although not shown, an upper pin 230 maycouple the root portion clevis 220 to the upper lug 234. A similararrangement may be provided for coupling the lower lugs 236 of the lowerwinglet attachment portion 184 to the root portion devises 220. Asindicated above, an arresting feature 238 may be incorporated into theroot portion clevis 220 and the upper lug 234 to prevent rotation of theupper lug 234 relative to the root portion clevis 220. In the embodimentshown, the arresting feature 238 may comprise a lug bearing portion 240formed on the upper lug 234 and a mating clevis bearing portion 242(FIGS. 16-17) that may be formed on the root portion clevis 220, andwhich may be disposed in abutting contact with one another when the lugs234, 236 are coupled to the root portion devises 220 by means of theshear pins 262 (FIG. 22).

FIG. 19 illustrates an embodiment of the upper pin 230 coupling theupper winglet attachment portion 176 to the root portion clevis 220extending outwardly from the fitting root end 154 (FIG. 18). The upperpin 230 may include a retaining pin 224 that may extend through a centerof the upper pin 230. Retaining clips 228 may be mounted on oppositesides of the root portion clevis 220. A nut 226 may be secured on oneend of the retaining pin 224. The center pin 222 (FIG. 16) and the lowerpins 232 (FIG. 16) may include retaining pins 224 and retaining clips228 similar to the arrangement of the upper pin 230 illustrated in FIG.19. In an embodiment, the center pin 222 may be provided in a largerdiameter than the upper pin 230 and the lower pin 232 to accommodatelarger shear loads in the center pin 222.

FIGS. 20-21 shown is an embodiment of the winglet attach fitting 150which may be configured similar to the winglet attach fitting 150embodiments shown in FIGS. 14-15 and described above, but wherein thefitting root end 154 of the wing attachment portion 152 in FIGS. 20-21is integral 244 with the wing tip rib 128. In this regard, the wingattachment portion 152 may be configured to be attached to an end of oneor more wing spars 116. For example, in the embodiment shown, theintegral wing attachment portion 152/wing tip rib 128 may be fastened tothe wing forward spar 118 and wing aft spar 120. Advantageously, for theembodiment shown in FIGS. 20-21, the integration of the wing attachmentportion 152 with the wing tip rib 128 results in a significant reductionin mass relative to a separately-formed wing attachment portion 152 andwing tip rib 128. The significant reduction in mass of the integral wingattachment portion 152/wing tip rib 128 is due to the elimination ofbarrel nuts 168 (FIG. 16) and the bearing material in the winglet attachfitting 150 surrounding the barrel nuts 168 for transferring load fromthe upper and lower winglet 300, 400 to the wing tip rib 128.

A further advantage provided by the integral wing attachment portion152/wing tip rib 128 of FIGS. 20-21 is an elimination of the need toaccess the wing interior 132 for one-sided installation of tensionfasteners 172. The need to access the wing interior 132 is eliminated bythe ability to remove the upper winglet 300 and/or the lower winglet 400by removing the upper and/or lower pins 230, 232 and center pins 222 asmentioned above. The integrally-formed wing attachment portion 152/wingtip rib 128 may be implemented on any one of the winglet attach fittings150 disclosed herein.

FIG. 22 illustrates a further embodiment of a winglet attach fitting 150wherein the wing attachment portion 152 and the upper winglet attachmentportion 176 are formed as a unitary structure and the lower winglet 400attachment potion may be separately joined to the wing attachmentportion 152 using shear pins 262. The wing attachment portion 152 mayinclude a fitting root end 154 that may be configured similar (e.g.,with barrel nuts 168, mechanical fasteners, or other threadedreceptacles) to the fitting root end 154 of the above-described wingletattach fittings 150. The upper winglet 300 may be fastened to the upperwinglet attachment portion 176 using skin spices 264 and/or spar splices266. The lower winglet 400 may be coupled to the lower wingletattachment portion 184 using clevis fittings 254, 256 which may allowfor removably fastening the lower winglet 400 to the wing attachmentportion 152.

FIG. 23 shows an exploded view of the winglet attach fitting 150 of FIG.22 and illustrating a plurality of the skin splices 264 and a pluralityof spar splices 266 for coupling the upper winglet 300 to the upperwinglet attachment portion 176. The lower winglet attachment portion 184may also be integral with the upper winglet attachment portion 176, andmay include one or more lugs 250, 252 extending outwardly from the lowerwinglet attachment portion 184. For example, FIG. 23 illustrates aforward lug 250 and an aft lug 252 extending from the lower wingletattachment portion 184.

In FIG. 23, shown are clevis fittings 254, 256 for coupling the lowerwinglet 400 to the lower winglet attachment portion 184. In anembodiment, the clevis fittings 254, 256 may be fastened to the lowerwinglet 400. The clevis fittings may comprise a forward clevis fitting254 and an aft clevis fitting 256 for respectively coupling to a forwardlug 250 and an aft lug 252 of the lower winglet attachment portion 184using shear pins 262. In an embodiment, each clevis fitting 254, 256 maybe coupled to a lug 250, 252 with a pair of shear pins 262 that may beextended through pin bores 202 formed in the clevis fittings 254, 256and lugs 250, 252. By providing at least two shear pins 262 in at leastone of the clevis/lug connections, the angular orientation of the lowerwinglet 400 may be non-rotatably fixed relative to the wing tip 114. Inan embodiment, the shear pins 262 may be configured to shear at apredetermined shear load to allow for separation of the lower winglet400 without damage to the wing 112 in the event of impact of the lowerwinglet 400 with an object.

Referring to FIG. 24, shown is a cross-section of the winglet attachfitting 150 of FIG. 23 coupling the upper winglet 300 and the lowerwinglet 400 to the wing tip 114. The wing attachment portion 152 may befastened to the wing tip rib 128 using tension fasteners 172 which maybe engaged to barrel nuts 168 contained within the fitting root end 154of the wing attachment portion 152 similar to the above-describedarrangements illustrated in FIGS. 9 and 13. The skin splices 264 may beinstalled against the inner surface of the upper winglet skin 314 andfastened to the upper winglet skin 314 using shear fasteners 174 such aslock bolts or other fasteners. Spar splices 266 may be installed againstthe surfaces of the winglet spars 310, 312, 314. The spar splices 266and winglet spars 310, 312, 314 may be fastened together usingmechanical fasteners.

Referring to FIG. 25, shown are the skin splices 264 and spar splices266 fastened to the upper winglet 300. The skin splices 264 may befastened to the upper winglet skin 314 using one or more shear fasteners174. The spar splices 266 may be fastened to one or more of the wingletspars 310, 312, 314 using one or more mechanical fasteners. Although notshown, one or more of the splices may be configured as a combinationskin splice/spar splice and may be fastened to the upper winglet skin314 and/or one or more winglet spars 310, 312, 314 using mechanicalfasteners. In an embodiment, the skin splices 264 and the spar splices266 may be formed of a material that minimizes galvanic corrosion. Forexample, the skin splices 264 and the spar splices 266 may be formed oftitanium to minimize galvanic corrosion with a composite (e.g., carbonfiber epoxy) upper winglet 300. However, the skin splices 264 and thespar splices 266 may be formed of other materials such as aluminum,steel, or nonmetallic material.

In FIG. 25, the splice portion 260 of the clevis fittings may beinstalled against the inner surface of the upper winglet skin 314 and/orwinglet spars 310, 312, 314 and fastened thereto using mechanicalfasteners. The upper winglet 300 may be coupled to the upper wingletattachment portion 176 by inserting the skin splices 264 and sparsplices 266 into the terminal end 182 of the upper winglet attachmentportion 176 and securing with the mechanical fasteners. The lowerwinglet 400 may be coupled to the winglet attach fitting 150 by aligningthe clevis portion 258 of the clevis fittings 254, 256 with the lugs250, 252 extending outwardly from the lower winglet attachment portion184. Shear pins 262 may be inserted into the pin bores 202 tonon-rotatably fix the lower winglet 400 to the winglet attach fitting150.

In the embodiments shown in FIGS. 24-25, the skin splices 264 may beconfigured to act as doublers. For example, the walls 178 of the upperwinglet attachment portion 176 may be configured to overlap (not shown)the lower edges of the upper winglet skin 314 with one or two rows ofshear fasteners 174. The skin splices 264 may be fastened to the overlapof the walls 178 of the upper winglet attachment portion 176 over theupper winglet skin 314, and the skin splices 264 may extend further intothe upper winglet 300 and pick up additional rows of shear fasteners174. Such an arrangement would assist in transferring load from theupper winglet 300 to the wing tip 114. A similar arrangement may beprovided for the lower winglet 400 wherein the walls 186 of the lowerwinglet attachment portion 184 may overlap a portion of the lowerwinglet skin 414 for one or two rows of shear fasteners 174, and theskin splices 264 may extend further into the lower winglet 400 to pickup additional rows of shear fasteners 174 to assist in transferring loadfrom the lower winglet 400 to the wing tip 114.

In any of the embodiments disclosed herein, the winglet attach fitting150 may be formed of a material that provides suitable strength andstiffness characteristics for attaching the upper winglet 300 and thelower winglet 400 to the wing tip 114. In an embodiment, the wingletattach fitting 150 may be formed of a metallic material such asaluminum, titanium, or other materials. However, the winglet attachfitting 150 may also be formed of a composite material (e.g., carbonfiber epoxy), or as a combination of composite material and metallicmaterial, or other material.

In FIG. 26, shown is a flowchart of an embodiment of a method 500 ofsecuring a split winglet 298 to a wing tip 114 of a wing 112.Advantageously, the method provides a means for attaching an upperwinglet 300 and a lower winglet 400 to a wing tip 114 of a wing 112 withone-sided access to the wing tip 114. In addition, the method provides ameans for removing the upper winglet 300 from the wing tip 114 withoutremoving the lower winglet 300, and removing the lower winglet 400 fromthe wing tip 114 without removing the upper winglet 300, and withoutseparating or detaching the winglet attach fitting 150 from the wing tip114.

Step 502 of the method 500 of FIG. 26 may include coupling an upperwinglet 300 to an upper winglet attachment portion 176 of a wingletattach fitting 150 having a wing attachment portion 152. For example, asshown in FIGS. 9, 13, and 14, the winglet attach fittings 150 areconfigured such that the upper winglet 300 may be stove-piped over theterminal end 182 of the upper winglet attachment portion 176. In theembodiment shown, shear fasteners 174 may be extended through the upperwinglet skin 314 and into the walls 178 of the terminal end 182 of theupper winglet attachment portion 176. In a further embodiment of thewinglet attach fitting 150 shown in FIG. 22, the upper winglet 300 maybe attached to the upper winglet attachment portion 176 by means of skinsplices 264 and/or spar splices 266 as mentioned above. The skin splices264 and/or spar splices 266 may be fastened to the upper winglet skin314 using shear fasteners 174. Mechanical fasteners may fasten the upperwinglet 300 spars to the spar splices 266.

Step 504 of the method 500 of FIG. 26 may include coupling the lowerwinglet 400 to the lower winglet attachment portion 184 of the wingletattach fitting 150. FIGS. 9, 13, and 14 illustrate an embodiment of thewinglet attach fitting 150 wherein the lower winglet 400 is stove-pipedover the terminal end 190 of the lower winglet attachment portion 184and secured with shear fasteners 174 extended through the lower wingletskin 414 and into the walls 186 of the terminal end 190 of the lowerwinglet attachment portion 184. In the embodiment of the winglet attachfitting 150 shown in FIG. 22, the upper winglet 300 may be attached tothe upper winglet attachment portion 176 by means of skin splices 264and/or spar splices 266 which may be fastened to the upper winglet 300using shear fasteners 174 installed through the upper winglet skin 314.Mechanical fasteners may be used to fasten the spar splices 266 to thewinglet spars 310, 312, 314.

In the embodiment of the winglet attach fitting 150 shown in FIGS.11-13, the upper winglet attachment portion 176 may be secured to thelower winglet attachment portion 184 by means of one or more hinge pins212. In an embodiment of the winglet attach fitting 150 shown in FIGS.15-21, the upper winglet attachment portion 176 may be secured to thelower winglet attachment portion 184 by means of center pins 222 andupper and lower pins 230, 232 extended through lugs 234, 236 and rootportions devises 220. For the winglet attach fitting 150 of FIGS. 15-21,the method may include placing one or more lug bearing portions 240 intobearing contact with the clevis bearing portions 242 of the devises 220to prevent rotation of the upper winglet 300 and/or the lower winglet400 after removing the center pin 222.

Step 506 of the method 500 of FIG. 26 may include fastening the wingattachment portion 152 to a wing tip 114 using tension fasteners 172. Asindicated above, the tension fasteners 172 may be passed into the winginterior 132 such as through an opening 125 covered by an access panel126 on the lower wing skin 124 as shown in FIG. 10. The tensionfasteners 172 may be inserted into fastener bores 170 in the wing tiprib 128 and threadably engaged to barrel nuts 168 or other threadedreceptacles contained within or mounted to the wing attachment portion152. Advantageously, the winglet attach fitting 150 allows for one-sidedinstallation of the tension fasteners 172 such as from an inboard side134 of the wing tip 114 for securing the split winglet 298 to the wing.

Step 508 of the method 500 of FIG. 26 may include removing the wingletattach fitting 150 from the wing 112 by removing the tension fasteners172 securing the wing attachment portion 152 to the wing tip 114. Thetension fasteners 172 may be accessed and/or removed through the opening125 in the wing skin 122, 124 and which may be covered by an accesspanel 126. For the embodiments of the winglet attach fitting 150 shownin FIGS. 5-6, 10-12, and 14-15, the removal of the tension fasteners 172may allow for removing the wing attachment portion 152 from the wing tip114 while the upper winglet 300 and/or the lower winglet 400 remainattached to the wing attachment portion 152.

For the embodiment of the winglet attach fitting 150 shown in FIGS.11-13, the method may include removing the hinge pin 212 attaching theupper winglet attachment portion 176 to the lower winglet attachmentportion 184, and removing the tension fasteners 172 securing the upperbracket 206 and/or the lower bracket 208 to the wing tip 114 as shown inFIG. 13. Following the removal of the tension fasteners 172, the methodmay further include removing the upper winglet 300 and/or the lowerwinglet 400 from the wing tip 114. For the embodiment of the wingletattach fitting 150 shown in FIGS. 14-15, the method may include removingthe center pins 222 interconnecting the upper lugs 234 of the upperwinglet attachment portion 176 with the lower lugs 236 of the lowerwinglet attachment portion 184 and the devises of the wing attachmentportion 152. The method may additionally include removing the upper pins230 and/or lower pins 232 (e.g., shear pins) securing the upper wingletattachment portion 176 and the lower winglet attachment portion 184 tothe devises 220, followed by removing the upper winglet 300 and/or thelower winglet 400 from the wing attachment portion 152.

For the embodiment of the winglet attach fitting 150 shown in FIGS.22-25, the method may include removing the shear pins 262 securing thefitting lugs 250, 252 of the lower winglet attachment portion 184 to theclevis fittings 254, 256 that may be fastened to the lower winglet 300.Following the removal of the shear pins 262, the method may includeremoving the lower winglet 400 from the wing attachment portion 152while the upper winglet 300 remains attached to the wing tip 114.Advantageously, the winglet attach fitting 150 shown in FIGS. 22-25allows for quickly removing and/or reinstalling the lower winglet 400 bythe removal of a relatively small quantity of shear pins 262 (e.g., four(4) shear pins).

Referring to FIG. 27, shown is a flow chart illustrating operations thatmay be included in a method 600 of using a winglet attach fitting 150.Step 602 of the method 600 may comprise providing an aircraft 100 havinga winglet attach fitting 150 that may attach a split winglet 298 to awing 112 (FIG. 2) of the aircraft 100 (FIG. 2). The split winglet 298may be attached to the aircraft 100 using any one of the above-describedembodiments of the winglet attach fitting 150 and which may beillustrated in the figures, and which may include other winglet attachfitting 150 embodiments within the scope of the present disclosure.

Step 604 of the method 600 of FIG. 27 may comprise maintaining thewinglet attach fitting 150 at a first height (not shown) relative to thefuselage (FIG. 2) when the aircraft 100 is non-flying such as when theaircraft 100 is on the ground and/or in a static position (not shown)such as parked at an airport terminal gate. In a static position, asubstantial majority of the weight of the aircraft 100 may be supportedby the aircraft landing gear (not shown) such that the wings 112 mayassume a slightly downwardly-deflected shape under a ground staticloading. The ground static loading on the wings 112 may be due togravitational force acting on the mass of the wing structure, fuel, thepropulsion units, and/or other systems that may be supported by thewings 112.

Step 606 of the method 600 of FIG. 27 may comprise moving the wingletattach fitting 150 to a second height (not shown) relative to thefuselage (FIG. 2) when the aircraft 100 is flying and wherein the secondheight is higher than the first height. The movement of the wingletattach fitting 150 from the first height to the second height may occuras a result of aeroelastically upward deflection of the wings 112 suchas under an approximate 1-g flight loading. The upward deflection of thewings 112 may cause the wing tips 114, the wing attach fittings 150,and/or the split winglets 298 to move upwardly toward the second height.The movement of the winglet attach fitting 150 toward the second heightmay occur when at least a portion of the weight of the aircraft 100 issupported by the wings 112 such as during takeoff from a runway, duringclimb-out, during level cruise flight, or during any other portion of aflight wherein at least a portion of the aircraft 100 weight issupported by the wings 112.

Referring to FIGS. 28-29, embodiments of the disclosure may be describedin the context of an aircraft manufacturing and service method 700 asshown in FIG. 28 and an aircraft 702 as shown in FIG. 29. Duringpre-production, exemplary method 700 may include specification anddesign 704 of the aircraft 702 and material procurement 706. Duringproduction, component and subassembly manufacturing 708 and systemintegration 710 of the aircraft 702 takes place. Thereafter, theaircraft 702 may go through certification and delivery 712 in order tobe placed in service 714. While in service by a customer, the aircraft702 is scheduled for routine maintenance and service 716 (which may alsoinclude modification, reconfiguration, refurbishment, and so on).

Each of the processes of method 700 may be performed or carried out by asystem integrator, a third party, and/or an operator (e.g., a customer).For the purposes of this description, a system integrator may includewithout limitation any number of aircraft manufacturers and major-systemsubcontractors; a third party may include without limitation any numberof vendors, subcontractors, and suppliers; and an operator may be anairline, leasing company, military entity, service organization, and soon.

As shown in FIG. 29 the aircraft 702 produced by exemplary method 700may include an airframe 718 with a plurality of systems 720 and aninterior 722. Examples of high-level systems 720 include one or more ofa propulsion system 724, an electrical system 726, a hydraulic system728, and an environmental system 730. Any number of other systems may beincluded. Although an aerospace example is shown, the principles of thedisclosed embodiments may be applied to other industries, such as theautomotive industry.

Apparatus and methods embodied herein may be employed during any one ormore of the stages of the production and service method 700. Forexample, components or subassemblies corresponding to production process708 may be fabricated or manufactured in a manner similar to componentsor subassemblies produced while the aircraft 702 is in service. Also,one or more apparatus embodiments, method embodiments, or a combinationthereof may be utilized during the production stages 708 and 710, forexample, by substantially expediting assembly of or reducing the cost ofan aircraft 702. Similarly, one or more of apparatus embodiments, methodembodiments, or a combination thereof may be utilized while the aircraft702 is in service, for example and without limitation, to maintenanceand service 716.

Additional modifications and improvements of the present disclosure maybe apparent to those of ordinary skill in the art. Thus, the particularcombination of parts described and illustrated herein is intended torepresent only certain embodiments of the present disclosure and is notintended to serve as limitations of alternative embodiments or deviceswithin the spirit and scope of the disclosure.

What is claimed is:
 1. A method of using a split winglet, comprisingsteps of: providing an aircraft having a winglet attach fittingattaching a split winglet to a wing of the aircraft, the split winglethaving an upper winglet and a lower winglet, the upper winglet having anupper winglet root chord, the lower winglet having a lower winglet rootchord, the winglet attach fitting configured such that the upper wingletroot chord at least partially overlaps the lower winglet root chord whenthe aircraft is viewed from a top-down perspective, the winglet attachfitting including: a wing attachment portion coupled to a wing tip ofthe wing; an upper winglet attachment portion coupled to the wingattachment portion and supporting the upper winglet; a lower wingletattachment portion coupled to the winglet attachment portion andsupporting the lower winglet; maintaining the winglet attach fitting andwinglet at a first height relative to a fuselage when the aircraft isnon-flying; and moving the winglet attach fitting and winglet to asecond height relative to the fuselage when the aircraft is flying, thesecond height being higher than the first height.
 2. The method of claim1, wherein maintaining the winglet attach fitting and winglet at thefirst height when the aircraft is non-flying includes: assuming aslightly downwardly-deflected shape of the wing under a ground staticloading.
 3. The method of claim 1, wherein moving the winglet attachfitting and winglet to the second height when the aircraft is flyingincludes: aeroelastically upwardly deflecting the wing when the aircraftis flying.
 4. The method of claim 1, wherein: at least one of the upperwinglet attachment portion and the lower winglet attachment portion isstove-piped into a respective one of the upper winglet and the lowerwinglet.
 5. The method of claim 1, wherein: the wing attachment portionis attached to a wing tip with tension fasteners.
 6. The method of claim1, wherein: the wing attachment portion includes a wing tip rib that isintegral with the wing attachment portion; and the wing tip rib iscoupled to at least one wing spar of the wing.
 7. The method of claim 1,wherein: the upper winglet is attached to the upper winglet attachmentportion using shear fasteners; and the lower winglet is attached to thelower winglet attachment portion using shear fasteners.
 8. The method ofclaim 1, wherein: the wing attachment portion is comprised of an upperbracket and a lower bracket; the upper bracket being integral with theupper winglet attachment portion; the lower bracket being integral withthe lower winglet attachment portion; the upper bracket and the upperwinglet attachment portion being a separate component from the lowerbracket and the lower winglet attachment portion; and the upper bracketand upper winglet attachment portion being hingedly coupled to the lowerbracket and lower winglet attachment portion by a hinge pin extendingthrough pin bores formed in hinge bosses extending from the upperbracket and the lower bracket.
 9. The method of claim 1, wherein: thewing attachment portion, the upper winglet attachment portion, and thelower winglet attachment portion are separate components that arecoupled together with pins.
 10. The method of claim 1, wherein: theupper winglet attachment portion and the lower winglet attachmentportion each include at least one lug; the wing attachment portionincluding at least one clevis; and the lug of the upper wingletattachment portion and the lug of the lower winglet attachment portionbeing coupled to the clevis using at least one pin.
 11. The method ofclaim 10, wherein: the lug of the upper winglet attachment portion iscoupled to the clevis with a center pin and an upper pin; and the lug ofthe lower winglet attachment portion is coupled to the clevis with thecenter pin and a lower pin.
 12. The method of claim 11, wherein: thewing attachment portion includes an arresting feature preventingrotation of at least one of the upper winglet and lower winglet when thecenter pin is removed from the wing attachment portion.
 13. A method ofusing a split winglet, comprising the steps of: providing an aircrafthaving a winglet attach fitting attaching a split winglet to a wing ofthe aircraft, the split winglet having an upper winglet and a lowerwinglet, the upper winglet having an upper winglet root chord, the lowerwinglet having a lower winglet root chord, the winglet attach fittingconfigured such that the upper winglet root chord at least partiallyoverlaps the lower winglet root chord when the aircraft is viewed from atop-down perspective, the winglet attach fitting including: a wingattachment portion coupled to a wing tip of the wing; an upper wingletattachment portion coupled to the wing attachment portion and supportingthe upper winglet; a lower winglet attachment portion coupled to thewing attachment portion and supporting the lower winglet; at least oneof a skin splice and a spar splice coupling the upper winglet to theupper winglet attachment portion; at least one clevis fitting couplingthe lower winglet to a lug integrally formed with the lower wingletattachment portion; maintaining the winglet attach fitting and wingletat a first height relative to a fuselage when the aircraft isnon-flying; and moving the winglet attach fitting and winglet to asecond height relative to the fuselage when the aircraft is flying, thesecond height being higher than the first height.
 14. The method ofclaim 13, wherein the wing attach fitting includes: a shear pin couplingthe clevis fitting to the lug; and the shear pin configured to shear ata predetermined load on the lower winglet to allow the lower winglet toseparate from the wing prior to plastic deformation of the wing.
 15. Themethod of claim 13, wherein: at least one of the upper wingletattachment portion and the lower winglet attachment portion isstove-piped into a respective one of the upper winglet and the lowerwinglet.
 16. The method of claim 13, wherein: the wing attachmentportion is attached to the wing tip with tension fasteners.
 17. A methodof using a split winglet, comprising the steps of: providing an aircrafthaving a winglet attach fitting attaching a split winglet to a wing ofthe aircraft, the split winglet having an upper winglet and a lowerwinglet, the upper winglet having an upper winglet root chord, the lowerwinglet having a lower winglet root chord, the winglet attach fittingconfigured such that the upper winglet root chord at least partiallyoverlaps the lower winglet root chord when the aircraft is viewed from atop-down perspective, the winglet attach fitting including: a wingattachment portion coupled to a wing tip of the wing; an upper wingletattachment portion coupled to the wing attachment portion and supportingthe upper winglet; a lower winglet attachment portion coupled to thewing attachment portion and supporting the lower winglet; the upperwinglet attachment portion and the lower winglet attachment portion area single-piece, unitary structure; maintaining the winglet attachfitting and winglet at a first height relative to a fuselage when theaircraft is non-flying; and moving the winglet attach fitting andwinglet to a second height relative to the fuselage when the aircraft isflying, the second height being higher than the first height.
 18. Themethod of claim 17, wherein: at least one of the upper wingletattachment portion and the lower winglet attachment portion isstove-piped into a respective one of the upper winglet and the lowerwinglet.
 19. The method of claim 17, wherein: the wing attachmentportion is attached to the wing tip with tension fasteners.
 20. Themethod of claim 19, wherein: the wing attachment portion includes barrelnut bores configured to contain barrel nuts; and the tension fastenersare threadably engageable to the barrel nuts.